The technique of laser intensity correlation spectroscopy will be employed to measure the size distribution parameters of low and very low density lipoproteins (LDL and VLDL). These distributions will be obtained for the LDL and VLDL from normal individuals on normal diets and from individual members of carefully chosen families having classic familial Type II and Type IV hyperlipoproteinemias. Certain individuals having Type III will also be studied in this manner. Comparisons among these measurements will: 1) indicate the normal variability of the distributional parameters (i.e., mean size and variance); 2) show whether the size distributions differ among hyperlipemic individuals, normal members of the hyperlipemic families and normals in the general population. The accuracy of the intensity correlation technique will also be exploited to study the effect of various structural modifications on the conformation and configuration of LDL in solution by determining their influence on the size distribution parameters. Among these modifications will be treatment with phospholipases, removal of neutral lipids, succinylation, iodination and incorporation of cholestrol. Finally we intend to determine the effect of the various techniques which have been used to solubilize apo-LDL on both its diffusion coefficient and the degree of polydispersity of these particles. The weight average molecular weight will also be determined from light scattering intensity measurements. In this manner, any molecular weight differences, mean particle size differences or different amounts of polydispersity which may occur can be ascribed to differences in preparation since the same physical method is used to characterize each sample.